A system always comprises at least one receiver for receiving signals. Conventionally, the receiver may need to operate at different operation speeds to support different specifications. However, the receiver needs to operate in a suitable reference voltage range such that it can operate at a desired operation speed.
FIG.1 is a schematic diagram illustrating operations for a conventional receiver. As illustrated in FIG.1, if the receiver is desired to operate at an operation speed 2.7 Gbps to meet the requirements of Standard 1, it needs to operate at a reference voltage equaling to or higher than 0.9v, or the operation performance for the receiver will be bad. Similarly, if the receiver is desired to operate at an operation speed 1.9 Gbps to meet the requirements of Standard 2, it needs to operate at a reference voltage equaling to or higher than 0.6v, or the operation performance for the receiver will be bad.
In another example in FIG. 1, the receiver is desired to operate at an operation speed of 3.2 Gbps to meet the requirements of Standard 3. However, the reference voltage is too low, such that the receive can only operate at an operation speed of 1.6 Gbps, thus the performance for the receiver is bad.
Accordingly, if the reference voltage tolerance range is too narrow, which indicates the range that the receiver can have good operation is too narrow, the performance for the receiver may always be non-optimized.